(a) Field of the Invention
The present invention relates to a current generating circuit. More particularly, the present invention relates to a circuit that supplies a constant current by stably operating during a temperature change.
(b) Description of the Related Art
In general, a circuit of electronic equipment is formed as a plurality of active and passive elements or as a chip in which an active element and a passive element are integrated. Each element constituting such electronic equipment requires a bias circuit that can provide a constant reference voltage or reference current for stable operation of the electronic equipment. Therefore, in an electronic equipment, a circuit that generates reference bias is an essential element.
Elements that are included in an electronic equipment have different characteristics based on temperature. For example, passive elements such as a resistor or an inductor have a characteristic that resistance increases proportional to an increase in temperature, when a temperature increases in elements such as a diode or a transistor, semiconductor elements having specific bonding has a resistance value inversely proportional to the temperature. A characteristic of such an element may be linear or non-linear. Therefore, a reference bias circuit has an influence on temperature characteristics. Temperature increase due to an external portion and an internal temperature increase due to internal integration of a chip may have a negative influence on a performance of an electronic equipment. Therefore, bias circuits are preferably less sensitive to rapid increases in temperature characteristics.
Particularly, in an integrated circuit that is formed with a semiconductor element, an area integration degree of a circuit is wide by using CMOS technology and is thus used in several fields, but stability of a driving operation is determined according to physical characteristics of a CMOS transistor. A typical factor of a change of physical characteristics is a temperature change.
A current source circuit included in semiconductor circuits determines an operating point (bias) of a transistor, which is a basic element of a semiconductor circuit. A CMOS transistor existing within a semiconductor circuit mirrors a reference current in which a current source circuit supplies current with a predetermined ratio and determines an operating point of the CMOS transistor using the mirrored current. Therefore, to stably perform a constant operation of a semiconductor circuit, it is essential in improving a performance of the semiconductor circuit to supply a uniform constant current regardless of a temperature change.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.